The present invention relates to a locking gear drive and more particularly a locking gear drive incorporated into a protective roll-type shutter or awning device.
Security type shutters and awnings comprising a plurality of slats made of extruded aluminum, or other material, hingedly interlocked at each edge, and which can be rolled away by winding around a drum or about a rotatable shaft, are generally provided with a gear drive for the drum or rotatable shaft. Such an arrangement is disclosed, for example, in U.S. Pat. No. 4,294,302 assigned to the same assignee as the present application.
Gear drives for the rotatable shaft of a shutter or awning device generally have a driveshaft which is capable of being directly driven in rotation by a hand crank, or by a second shaft in turn hand or power driven through a second gear drive. The gear drive is enclosed in a housing, and the driven shaft and driving shaft are generally coupled by means of a pair of gears having their axes of rotation disposed in planes at right angles to each other. The gears are usually of the bevel type and provide a one-to-one gear ratio. As such a gear drive is reversible, some locking means must be provided so that the shutter can be maintained in a rolled-up position, or in any intermediate position from completely rolled-up to fully rolled-down.
Means for preventing the reverse rotation of gear drives incorporated in roll-type shutter or awning assemblies are known in the prior art. For example, in the above-mentioned U.S. Pat. No. 4,294,302, a positive locking mechanism for a gear drive incorporating bevel gears is disclosed which comprises a compression spring urging two sets of mating teeth into engagement with each other. One set of teeth is formed integrally with a portion of the interior of a gear box housing. The other set of teeth is disposed around the periphery of the driveshaft proximate one end. When both sets of mating teeth are engaged, the driving and driven shafts are held against rotation.
In such a configuration, the teeth on the driving shaft and within the gear box housing are disengaged by a driving handle or crank being pressed into a handle socket affixed at the end of the driving shaft projecting from the gear box. The driving handle longitudinally displaces the driving shaft against the pressure of the spring, thereby disengaging the mating teeth on the shaft from the teeth within the housing. Rotation of the unlocked driving shaft by the driving handle can thereafter be performed for raising or lowering the shutter.
Co-pending application Ser. No. 362,523, assigned to the same assignee as the present application, also discloses a locking mechanism for a gear drive such as the gear drive of a roll-type shutter or awning. In the gear drive of the co-pending application, one of the gear shafts, preferably the driving gear shaft, is rotatably supported such as to be longitudinally displaceable and carries at its free end a transverse pin. A stationary member disposed proximate the end of the shaft carrying the pin is provided with radial grooves. When the gear drive in is a locked position, the shaft is longitudinally displaced under the action of a coil spring such that at least one projecting end of the transverse pin is engaged in one of the radial grooves of the stationary member. The locking mechanism is unlocked by introducing the end of a crank handle into a coupling socket mounted on the other end of the shaft, and applying longitudinal pressure with the crank handle, thereby disengaging the pin from the grooves and permitting the shaft to be hand-driven in rotation by the crank handle.
As mentioned, both of the examples of locking means for a gear drive may be unlocked, for example, by the introduction of a crank handle into a socket. Longitudinal pressure applied to the handle disengages the respective interlockable components. It is preferable, in addition, that a locking gear drive be designed such that it is easily provided with a key-lock installation which prevents an unauthorized user from operating the gear drive by the mere acquisition of a suitable hand crank. Moreover, such a key-lock installation is most suitable wherein the turning of a key prevents the rotation of one shaft, or the other, of a gear drive, at the user's discretion.